# Fisher SAH CT grade (1980)

Fisher

Status: LIVE
Price: $0.005 USDC
`GET /api/calc/fisher`
HTML: https://magentlab.com/docs/fisher
Markdown: https://magentlab.com/docs/fisher.md

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

## What it computes

Return the Fisher 1980 original CT group 1-4 from a caller-assigned grade, with the published group description.

## When to use

When an agent needs the original Fisher 1980 CT groups 1-4 and must not invent modified Fisher 2006 grades or a linear vasospasm-risk percentage.

## When not to use

- Not a diagnosis and not a medical device. magent does not read the CT.
- This is Fisher 1980 original groups 1-4 only. It does not implement modified Fisher (Frontera 2006).
- Group 3 (thick SAH: localized clots and/or vertical layers ≥1 mm) was the high-vasospasm group in 1980. Group 4 is diffuse or no subarachnoid blood with ICH or IVH — not a worse grade than 3. magent does not invent a linear vasospasm risk from the integer.

## Formula

```
Fisher 1980 original CT group 1-4 as assigned by the caller
```

## Citation

[Relation of cerebral vasospasm to subarachnoid hemorrhage visualized by computerized tomographic scanning](https://doi.org/10.1227/00006123-198001000-00001)
Fisher CM, Kistler JP, Davis JM
Neurosurgery. 1980;6(1):1-9
DOI: [10.1227/00006123-198001000-00001](https://doi.org/10.1227/00006123-198001000-00001)

## Worked example

### Group 1 no blood detected

Given: `grade=1`

1. grade 1 → no blood detected


## Also searched as

- Fisher grade
- Fisher scale
- Fisher CT grade
- Fisher 1980
- SAH CT grade
- subarachnoid hemorrhage CT grade
- Fisher group
- original Fisher scale

## Parameters

- `grade` (integer, required): Fisher 1980 original CT group 1-4 as assigned by the caller from CT. magent does not read the CT.

## 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/fisher`
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": [
    {
      "grade": "1"
    },
    {
      "grade": "1"
    }
  ]
}
```

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

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/fisher",
  "items": [
    {
      "description": "No blood detected",
      "components": [
        {
          "factor": "grade",
          "points": 1,
          "present": true
        }
      ],
      "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.",
      "citation": {
        "authors": "Fisher CM, Kistler JP, Davis JM",
        "doi": "10.1227/00006123-198001000-00001",
        "id": "fisher-1980",
        "pmid": "7354892",
        "source": "Neurosurgery. 1980;6(1):1-9",
        "title": "Relation of cerebral vasospasm to subarachnoid hemorrhage visualized by computerized tomographic scanning"
      },
      "formula": "fisher",
      "formula_expression": "Fisher 1980 original CT group 1-4 as assigned by the caller",
      "max_score": 4,
      "score": 1,
      "grade": 1
    },
    {
      "description": "No blood detected",
      "components": [
        {
          "factor": "grade",
          "points": 1,
          "present": true
        }
      ],
      "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.",
      "citation": {
        "authors": "Fisher CM, Kistler JP, Davis JM",
        "doi": "10.1227/00006123-198001000-00001",
        "id": "fisher-1980",
        "pmid": "7354892",
        "source": "Neurosurgery. 1980;6(1):1-9",
        "title": "Relation of cerebral vasospasm to subarachnoid hemorrhage visualized by computerized tomographic scanning"
      },
      "formula": "fisher",
      "formula_expression": "Fisher 1980 original CT group 1-4 as assigned by the caller",
      "max_score": 4,
      "score": 1,
      "grade": 1
    }
  ]
}
```

## Response fields

- `formula` (string): fisher
- `formula_expression` (string): Published group rule
- `grade` (integer): Caller-assigned Fisher 1980 group 1-4
- `score` (integer): Same as grade
- `max_score` (integer): 4
- `description` (string): 1980 wording for that group
- `components` (array): Assigned-grade component
- `citation` (object): Fisher 1980
- `disclaimer` (string): Not a medical device

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "description": "No blood detected",
  "components": [
    {
      "factor": "grade",
      "points": 1,
      "present": true
    }
  ],
  "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.",
  "citation": {
    "authors": "Fisher CM, Kistler JP, Davis JM",
    "doi": "10.1227/00006123-198001000-00001",
    "id": "fisher-1980",
    "pmid": "7354892",
    "source": "Neurosurgery. 1980;6(1):1-9",
    "title": "Relation of cerebral vasospasm to subarachnoid hemorrhage visualized by computerized tomographic scanning"
  },
  "formula": "fisher",
  "formula_expression": "Fisher 1980 original CT group 1-4 as assigned by the caller",
  "max_score": 4,
  "score": 1,
  "grade": 1
}
```

## Errors

- HTTP 400 `invalid_fisher_grade`: grade must be an integer from 1 to 4 (Fisher 1980 groups). 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

- [Hunt-Hess](https://magentlab.com/docs/hunt-hess) — Return the Hunt and Hess 1968 subarachnoid-hemorrhage surgical-risk grade from a caller-assigned grade 1-5, applying the paper's next-less-favorable bump when serious systemic disease is present.
- [Ottawa SAH Rule](https://magentlab.com/docs/ottawa-sah) — Apply the Perry 2013 Ottawa SAH Rule and return whether investigation is indicated from age and five caller-assigned high-risk findings.

## Payment

Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, 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 accepts[0] (exact, EIP-3009) with validBefore = now + maxTimeoutSeconds (600 seconds), or accepts[1] (batch-settlement deposit/voucher) on product GET. Ping and POST {items} stay exact. Magent retries transient facilitator 429/5xx before answering.
- Retry the same URL with PAYMENT-SIGNATURE (base64 JSON echoing accepted, payload, and extensions when present).
- Success is HTTP 200 JSON plus PAYMENT-RESPONSE. exact settles before the tool. batch-settlement verifies (and deposit-settles) before the tool and commits the charge after HTTP 2xx. HTTP 503: retry the same PAYMENT-SIGNATURE. Mint a new exact 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.
- offered `batch-settlement` on eip155:8453: Payment-channel vouchers claimed later in batches. Exact stays accepts[0]. Same-path POST {items} is still exact. extra.assetTransferMethod=eip3009 extra.paymentFlow=authorization.

- 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.

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

- HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged.
- exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. 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.