# New Orleans Head CT Rule

New Orleans Head CT Rule

Status: LIVE
Price: $0.005 USDC
`GET /api/calc/new_orleans_head`
HTML: https://magentlab.com/docs/new-orleans-head
Markdown: https://magentlab.com/docs/new-orleans-head.md

Not a medical device. Not a diagnosis, dose, or listing recommendation.

## What it computes

Apply the Haydel 2000 New Orleans Head CT Rule and return whether CT is indicated from age and six caller-assigned findings after minor head injury.

## When to use

When an agent has caller-assigned findings after minor head injury in an adult with GCS 15 as published and needs the New Orleans (Charity) Head CT Rule, not the Canadian CT Head Rule and not PECARN.

## When not to use

- Not a diagnosis of brain injury. magent does not examine the patient.
- The published rule is GCS 15 minor head injury in adults. magent does not take GCS; the caller assigns the clinical flags.
- This tool is the Haydel 2000 New Orleans / Charity Head CT Rule only. It is not the Canadian CT Head Rule, not PECARN, and not a pediatric head-CT rule.

## Formula

```
ct indicated if any of headache, vomiting, age > 60, drug_or_alcohol_intoxication, short_term_memory_deficit, trauma_above_clavicles, or seizure
```

## Citation

[Indications for computed tomography in patients with minor head injury](https://doi.org/10.1056/NEJM200007133430204)
Haydel MJ, Preston CA, Mills TJ, Luber S, Blaudeau E, DeBlieux PM
N Engl J Med. 2000;343(2):100-105
DOI: [10.1056/NEJM200007133430204](https://doi.org/10.1056/NEJM200007133430204)

## Worked example

### All findings absent

Given: `age=40, drug_or_alcohol_intoxication=false, headache=false, seizure=false, short_term_memory_deficit=false, trauma_above_clavicles=false, vomiting=false`

1. Age 40 is not >60; all six clinical flags false
2. CT is not indicated


### Age 61 meets the age criterion

Given: `age=61, drug_or_alcohol_intoxication=false, headache=false, seizure=false, short_term_memory_deficit=false, trauma_above_clavicles=false, vomiting=false`

1. Age >60 is a CT indication (60 does not)
2. CT is indicated


### Headache alone

Given: `age=40, drug_or_alcohol_intoxication=false, headache=true, seizure=false, short_term_memory_deficit=false, trauma_above_clavicles=false, vomiting=false`

1. Age 40 does not meet the age criterion
2. Headache is present
3. CT is indicated


## Also searched as

- New Orleans Head CT Rule
- New Orleans Criteria
- Charity Head CT Rule
- Haydel head CT
- Haydel 2000
- NOC head CT
- New Orleans Criteria for CT
- Charity Hospital head CT rule

## Parameters

- `age` (integer, required): Age in years (18-120). Age >60 is a CT indication; 60 does not. The published rule is GCS 15 minor head injury in adults; magent does not take GCS.
- `headache` (boolean, required): Headache. true or false as assigned by the caller.
- `vomiting` (boolean, required): Vomiting. true or false as assigned by the caller.
- `drug_or_alcohol_intoxication` (boolean, required): Drug or alcohol intoxication. true or false as assigned by the caller.
- `short_term_memory_deficit` (boolean, required): Deficit in short-term memory (anterograde amnesia). true or false as assigned by the caller.
- `trauma_above_clavicles` (boolean, required): Physical evidence of trauma above the clavicles. true or false as assigned by the caller.
- `seizure` (boolean, required): Seizure. true or false as assigned by the caller.

## Bulk (POST)

POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

Method: `POST /api/calc/new_orleans_head`
Max items: 25
Price: unit_amount + extra_item_amount * (n - 1) (unit 5000 atomic, extra 2000 atomic)
Status: PREVIEW

- 1 to 25 items. Each item uses the same keys as the GET query parameters.
- POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows.
- The first invalid item fails the whole request (index in the 400 JSON). You are not charged.
- HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row.
- Catalog misses (empty matches, found=false) stay paid 200s inside that slot.
- x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items.

Example request:

```json
{
  "items": [
    {
      "age": "40",
      "drug_or_alcohol_intoxication": "false",
      "headache": "false",
      "seizure": "false",
      "short_term_memory_deficit": "false",
      "trauma_above_clavicles": "false",
      "vomiting": "false"
    },
    {
      "age": "40",
      "drug_or_alcohol_intoxication": "false",
      "headache": "false",
      "seizure": "false",
      "short_term_memory_deficit": "false",
      "trauma_above_clavicles": "false",
      "vomiting": "false"
    }
  ]
}
```

Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/new-orleans-head

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/new_orleans_head",
  "items": [
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "age_years": 40,
      "citation": {
        "authors": "Haydel MJ, Preston CA, Mills TJ, Luber S, Blaudeau E, DeBlieux PM",
        "doi": "10.1056/NEJM200007133430204",
        "id": "haydel-2000",
        "source": "N Engl J Med. 2000;343(2):100-105",
        "title": "Indications for computed tomography in patients with minor head injury"
      },
      "formula": "new_orleans_head",
      "formula_expression": "ct indicated if any of headache, vomiting, age > 60, drug_or_alcohol_intoxication, short_term_memory_deficit, trauma_above_clavicles, or seizure",
      "criteria": [
        {
          "factor": "headache",
          "met": false
        },
        {
          "factor": "vomiting",
          "met": false
        },
        {
          "value": 40,
          "factor": "age_gt_60",
          "met": false
        },
        {
          "factor": "drug_or_alcohol_intoxication",
          "met": false
        },
        {
          "factor": "short_term_memory_deficit",
          "met": false
        },
        {
          "factor": "trauma_above_clavicles",
          "met": false
        },
        {
          "factor": "seizure",
          "met": false
        }
      ],
      "ct_indicated": false
    },
    {
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "age_years": 40,
      "citation": {
        "authors": "Haydel MJ, Preston CA, Mills TJ, Luber S, Blaudeau E, DeBlieux PM",
        "doi": "10.1056/NEJM200007133430204",
        "id": "haydel-2000",
        "source": "N Engl J Med. 2000;343(2):100-105",
        "title": "Indications for computed tomography in patients with minor head injury"
      },
      "formula": "new_orleans_head",
      "formula_expression": "ct indicated if any of headache, vomiting, age > 60, drug_or_alcohol_intoxication, short_term_memory_deficit, trauma_above_clavicles, or seizure",
      "criteria": [
        {
          "factor": "headache",
          "met": false
        },
        {
          "factor": "vomiting",
          "met": false
        },
        {
          "value": 40,
          "factor": "age_gt_60",
          "met": false
        },
        {
          "factor": "drug_or_alcohol_intoxication",
          "met": false
        },
        {
          "factor": "short_term_memory_deficit",
          "met": false
        },
        {
          "factor": "trauma_above_clavicles",
          "met": false
        },
        {
          "factor": "seizure",
          "met": false
        }
      ],
      "ct_indicated": false
    }
  ]
}
```

## Response fields

- `formula` (string): new_orleans_head
- `formula_expression` (string): Haydel 2000 seven-factor CT indication rule
- `ct_indicated` (boolean): true when any of the seven published findings is present. Not a diagnosis.
- `age_years` (integer): Age used for the >60 criterion
- `criteria` (array): Per-factor rows with factor and met; age_gt_60 is computed from age (value is age_years)
- `citation` (object): Haydel 2000 N Engl J Med citation
- `disclaimer` (string): Not-a-device notice

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "age_years": 40,
  "citation": {
    "authors": "Haydel MJ, Preston CA, Mills TJ, Luber S, Blaudeau E, DeBlieux PM",
    "doi": "10.1056/NEJM200007133430204",
    "id": "haydel-2000",
    "source": "N Engl J Med. 2000;343(2):100-105",
    "title": "Indications for computed tomography in patients with minor head injury"
  },
  "formula": "new_orleans_head",
  "formula_expression": "ct indicated if any of headache, vomiting, age > 60, drug_or_alcohol_intoxication, short_term_memory_deficit, trauma_above_clavicles, or seizure",
  "criteria": [
    {
      "factor": "headache",
      "met": false
    },
    {
      "factor": "vomiting",
      "met": false
    },
    {
      "value": 40,
      "factor": "age_gt_60",
      "met": false
    },
    {
      "factor": "drug_or_alcohol_intoxication",
      "met": false
    },
    {
      "factor": "short_term_memory_deficit",
      "met": false
    },
    {
      "factor": "trauma_above_clavicles",
      "met": false
    },
    {
      "factor": "seizure",
      "met": false
    }
  ],
  "ct_indicated": false
}
```

## Errors

- HTTP 400 `invalid_age`: age must be an integer from 18 to 120 Returned before settlement; you are not charged.
- HTTP 400 `invalid_flag`: boolean clinical flags must be true or false Returned before settlement; you are not charged.
- HTTP 400 `invalid_items`: POST body must be a JSON object with only an items array Returned before settlement; you are not charged.
- HTTP 400 `invalid_item_count`: items must be an array of 1 to 25 objects Returned before settlement; you are not charged.
- HTTP 400 `invalid_item`: each items entry must be a JSON object Returned before settlement; you are not charged.

Shared HTTP 402 and 503: https://magentlab.com/docs/payments

## Related tools

- [Canadian CT Head Rule](https://magentlab.com/docs/canadian-ct-head) — Apply the Stiell 2001 Canadian CT Head Rule and return whether CT is indicated from caller-assigned high-risk and medium-risk findings after minor blunt head injury.
- [NEXUS C-spine](https://magentlab.com/docs/nexus) — Apply the Hoffman 2000 NEXUS C-spine rule and return whether the five low-risk criteria all hold (imaging not indicated by this rule).

## Payment

Required query parameters must be present and valid. Invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s.

- GET the tool with Accept: application/json (do not send Accept: text/html unless you want the human paywall).
- HTTP 402 means you have not paid. Decode the base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote.
- Sign EIP-3009 (scheme exact, assetTransferMethod eip3009) with validBefore = now + accepts[0].maxTimeoutSeconds (600 seconds). That window starts when you sign and must cover wallet confirmation plus CDP verify and settle. Magent retries transient facilitator 429/5xx before answering. Do not send upto or batch-settlement payloads; magent does not offer those schemes.
- Retry the same URL with PAYMENT-SIGNATURE (base64 JSON echoing accepted, payload, and extensions when present).
- Success is HTTP 200 JSON plus PAYMENT-RESPONSE. Settlement happens before the tool runs. HTTP 503 settlement_uncertain or settle_failed: retry the same PAYMENT-SIGNATURE. Mint a new nonce only after a new HTTP 402.

- offered `exact` on eip155:8453: Fixed-price USDC on Base. The buyer authorizes the advertised amount (EIP-3009). magent settles before the tool runs (paymentFlow upfront). extra.assetTransferMethod=eip3009 extra.paymentFlow=upfront.

- not offered `upto`: Not offered. Usage-based: buyer authorizes a ceiling, seller settles the actual amount after work. Reserved for a future metered tool. Not for current calculators or code search.
- not offered `batch-settlement`: Not offered. Payment-channel vouchers claimed later in batches. Not the same as POST {items} bulk (that is still exact).

Same-path POST {items} is still scheme exact: one EIP-3009 authorization for GET unit plus $0.002 per extra item. That is not x402 batch-settlement (payment channels / vouchers).

Shared HTTP 402 and 503 table: https://magentlab.com/docs/payments

Stdio MCP (one process per host): https://magentlab.com/docs/mcp

## Guarantees

- Invalid query parameters return HTTP 400 before settlement. You are not charged.
- Settlement finishes before the tool executes (paymentFlow upfront). Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE.
- HTTP 402 is unpaid only. Do not sign a second authorization because of a 503.
- Execution is timeout-bounded and concurrency-capped.
- Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.